1. Field of the Invention
The invention relates to an air mass flowmeter comprising a tube and a sensor module, which is fitted in the tube, for measuring a gas quantity flowing in a main direction of flow in the tube at a flow speed. The sensor module extends in the main direction of flow in the tube, a first end of the sensor module defines a first plane normal to the main direction of flow and a second end of the sensor module defines a second plane normal to the main direction of flow. The sensor module has a flow channel that receives some of the gas quantity flowing in the tube and directs said gas quantity via measuring elements.
In the context of the present application, the term “air” is used as an example for a gas or gas mixture, the mass flow of which can be determined. In principle, the air mass flowmeter according to embodiments of the invention can be used to determine the mass flow of any gas or gas mixture.
2. Description of Prior Art
Air mass flowmeters of this kind are known and are used in large numbers in motor vehicle construction to detect the air mass flowing to an internal combustion engine. Depending on the air mass flow detected by the air mass flowmeter, it is possible both to perform diagnostics, e.g. of the operation of the internal combustion engine, and to exercise control of the internal combustion engine. For these purposes, detection of the actual air mass flow in a manner which is reliable and as precise as possible, even under different operating conditions, is important.
EP 0 458 998 A1 discloses an air mass flowmeter having a housing in which a flow channel is formed and in which a flow straightener is inserted upstream of a sensor element. The flow straightener comprises a honeycomb body and a ring, which protrudes beyond the combs in the flow direction and in which a grill is embedded at a distance from the combs, producing microvortices. The grill has the disadvantage that, with prolonged operation of the air mass flowmeter under high vibrational loads, of the kind which often occur in the automotive engineering sector, it is subject to fatigue and may fail mechanically. Moreover, the insertion of the grill into the ring of the honeycomb body is complex and therefore expensive.